cbmem fails with `Failed to mmap /dev/mem: Resource temporarily unavailable` and code coverage enabled

[Paul Menzel]

Dear coreboot folks,

building a coreboot image for the ASRock E350M1 with the attached
config, having code coverage enabled, I am unable to run the utility
`cbmem`.

```
$ sudo util/cbmem/cbmem -V -l
Looking for coreboot table at 0 1048576 bytes.
Mapping 1MB of physical memory at 0x0 (requested 0x0).
Found!
  coreboot table entry 0x11
    Found forwarding entry.
Unmapping 1MB of virtual memory at 0xb74b6000.
Looking for coreboot table at c7f9f000 1048576 bytes.
Mapping 1MB of physical memory at 0xffffffffc7f9f000 (requested 0xc7f9f000).
  ... failed.  Mapping 1052671B of physical memory at 0xffffffffc7f9e000.
Failed to mmap /dev/mem: Resource temporarily unavailable
```

Linux complains with the messages below.

```
$ dmesg
[…]
[  916.233910] x86/PAT: cbmem:2647 conflicting memory types c7f9f000-c809f000 uncached-minus<->write-back
[  916.233927] x86/PAT: reserve_memtype failed [mem 0xc7f9f000-0xc809efff], track uncached-minus, req write-back
[…]
```

Thanks,

Paul

[1] http://review.coreboot.org/11729

[Aaron Durbin]

On Sun, Sep 27, 2015 at 2:54 PM, Paul Menzel
 wrote:
> Dear coreboot folks,
>
> building a coreboot image for the ASRock E350M1 with the attached
> config, having code coverage enabled, I am unable to run the utility
> `cbmem`.
> $ sudo util/cbmem/cbmem -V -l
> Looking for coreboot table at 0 1048576 bytes.
> Mapping 1MB of physical memory at 0x0 (requested 0x0).
> Found!
>   coreboot table entry 0x11
>     Found forwarding entry.
> Unmapping 1MB of virtual memory at 0xb74b6000.
> Looking for coreboot table at c7f9f000 1048576 bytes.
> Mapping 1MB of physical memory at 0xffffffffc7f9f000 (requested 0xc7f9f000).
>   ... failed.  Mapping 1052671B of physical memory at 0xffffffffc7f9e000.
> Failed to mmap /dev/mem: Resource temporarily unavailable
>
> Linux complains with the messages below.
> $ dmesg
> […]
> [  916.233910] x86/PAT: cbmem:2647 conflicting memory types c7f9f000-c809f000 uncached-minus<->write-back
> [  916.233927] x86/PAT: reserve_memtype failed [mem 0xc7f9f000-0xc809efff], track uncached-minus, req write-back
> […]

You are going to need to open the /dev/mem file w/ O_SYNC flags
because the kernel is marking that range of memory as uncacheable.
More info can be found here:
https://www.kernel.org/doc/Documentation/x86/pat.txt

# cat /sys/kernel/debug/x86/pat_memtype_list

would be helpful along  with this:

$ for i in /sys/firmware/memmap/*; do echo $(cat $i/type $i/start $i/end); done
> Thanks,
>
> Paul
> [1] http://review.coreboot.org/11729
>
> coreboot mailing list: [e-mail]
> http://www.coreboot.org/mailman/listinfo/coreboot